The present invention relates generally to fluid processing devices and more particularly to devices exceptionally well suited for batch and continuous processing of fluids, especially fluid food products.
The prior art includes a wide variety of devices designed for intimately mixing, emulsifying and/or homogenizing powders, granules and liquids. See, generally, U.S. Pat. Nos. 1,994,371, 2,436,767, 4,173,925, 4,395,133, 4,418,089 and 4,525,072. Typical of the mixing devices offered for commercial use are those commonly referred to as "Henschel" mixers manufactured by the Thyssen Henschel Company of West Germany. See, Generally, "Henschel Mixer, A Complete Survey", Brochure 1000E 8/83 BO, distributed by Purnell International, Houston, Tex. 77248. See also, U.S. Pat. Nos. 4,518,262, 4,176,966, 4,104,738 and 4,037,753. Henschel mixers generally include one or more rotating blades disposed at the base of a chamber and operative, if desired, to produce high shear forces in the material to be mixed as well as fluidizing effects on the material. A variety of Henschel mixer apparatus conformations are available which allow for cooling or heating of materials undergoing mixing.
Of interest to the background of the invention are continuous mixing devices such as those illustrated in U.S. Pat. Nos. 3,854,702 and 4,357,111 which have been designed to provide greater uniformity of temperature distribution within a material undergoing mixing. In brief, these devices include single and multiple mixing stages involving multiple mixing tools or blades and a variety of baffles operative to continuously reintroduce partially mixed materials into contact with the mixing tools.
Despite substantial research and development in the manufacture of devices for intimate mixing of materials, none of the designs extant in the art have adequately dealt with the problems of establishing of high degrees of uniformity of flow of materials within a mixing vessel so as to provide the desirable characteristic of uniformity of temperature distribution within the material (e.g., a fluid) undergoing mixing. A common undesirable characteristic of prior devices is the presence of multiple "dead zones" wherein the flow rate of fluids undergoing mixing is diminished (vis-a-vis the remainder of the fluid in the vessel) giving rise, e.g., to temperature differentials within the fluid. Attempts to solve such problems through introduction of scraper blades and baffles of various conformation have met with limited success because such components by definition interfere with the natural conformation of fluid flow which is imparted by the rotating blades and mixer tools, giving rise to eddies in the flow. Moreover, where fluids undergoing mixing are susceptible to physiochemical changes from liquid to solid forms at increased temperatures (e.g., proteins in solution undergoing heat denaturation and agglomeration) the presence of baffles and the like provides sites for collection and build-up of undesired product forms within the mixing vessel.
There thus continues to exist a need in the art for fluid processing apparatus of novel design which affords enhanced homogeneity in flow and temperature distribution within the material undergoing mixing treatment. Such apparatus would be especially useful in the food preparation arts wherein mechanical energy imparted by rotating blades and mixing tools gives rise to high shear forces and heat energy within proteinaceous fluids which may be susceptible to solidification, with consequent adverse effects on smoothness characteristics of end products.